Modelling survival from fieldwork data: a case study on the social bat Molossus molossus
-
Upload
yann-gager -
Category
Science
-
view
107 -
download
0
Transcript of Modelling survival from fieldwork data: a case study on the social bat Molossus molossus
Yann Gager
Modelling survival from fieldwork data:
a case study on the social bat Molossus molossus
Acknowledgements
Dina Dechmann Teague O’Mara
Olivier Gimenez Rachel Page
+ many fieldwork assistants
Many animals are social…but why?
Many animals are social…but why?
Balance of costsand benefits of group
living
Sociality in bats
Tropics
Group hunting?
Temperate zones (summer)
Social thermoregulation Group hunting
Social foraging in insectivorous bats
[Safi & Kerth 2007]
- Energetically limited (small size, flight + echolocation)
- Extreme specialization (narrow wings + ephemeral insects)
- Acoustic information transfer on site between roost members
How is survival related to group size ?
Group size
Su
rviv
al
- Survival benefits/costs associated with group living?
[Dechmann et al. 2010]
Collection of survival data
1350 animals transpondered
during regular captures
7 roosts with automated readers
1980 « days »
Capture-recapture
14 sites – 77 captures
Roost variation
Monthly variation
1a. Size of groups: spatial variation
2. Survival analyses (capture)
- Data: capture-recapture (285 adult females)
- Analysis: Cox-proportional hazard regression
- Results: Effect of marking year
Variable p
Marking year 0.00966 ***
Initial group size 0.33938
Mean group size 0.97945
Site 0.81306
GLOBAL 0.12201
3. Survival analyses (transponder-reader)
- Data: 4 sites followed over 15 months (59 adult females)
- Aim: Model monthly survival
- Analysis: Model comparison (Multi-state Mark-Recapture)
- Results: Group size as the best explanatory variable
Model QAICc ΔQAICc No. Of parameters
Group size 1546.1 0.0 20
Month 1583.6 19.5 28
Marking year 1773.6 209.5 8
. 1786.8 222.7 4
Site 1791.2 227.1 7
3. Survival analyses (transponder-reader)
To conclude
Conclusions
1- Survival benefits with increased group size
2- Constraints to medium groups
Perspectives:
- Effect of group size on foraging efficiency
- Relatedness between group members
Thank you!